Apparatus for applying small particles to articles in an electric field



July 25, 1967 HEYL ET AL 3,332,395

APPARATUS FOR APPLYING SMALL PARTICLES T0 ARTICLES IN AN ELECTRIC FIELD Filed Aug. 24, 1964 2 Sheets-Sheet 1 F/Gl INVENTORSJ GERHARD HEYL, GUNTER LUTTGENS,.ANTON SCHM/TZ,

ATTORNEYS July 25, 1967 G. HEYL ET AL 3,332,395

APPARATUS FOR APPLYING SMALL PARTICLES TO ARTICLES IN AN ELECTRIC FIELD Filed Aug. 24, 1964 2 Sheets-Sheet 2 n 25 low FIG. 2

INVENTORS.

GERHARD HEYL, GUNTER LUTTGENS, ANTON SCHM/TZ.

A TTORNE Y5 United States Patent This invention relates to an apparatus for applying small particles, e.g. flocks, to moving objects, e.g. supports which are coated with adhesive according to which the electrical flocking or fibre-coating field is limited on the one hand by a conveyor belt with a means electrical conductivity, which belt is guided over two conductive and earthed rollers arranged spaced from one another and over at least one conductive roller arranged between the said two rollers and is connected to a high voltage source, and on the other hand by a moving support, of which the conductive adhesive layer may be connected through an earthed coating device or through the support and rollers to the earthed pole of the high-voltage source. The fibres for the coating are supplied in well-proportioned manner in a field-free space to the conveyor belt, which conveys the fibres into the fibrecoating field.

With this arrangement, it has been found to be possible for the fibre-coating field to be adapted in very' advantageous manner to different coating conditions, and more especially coating fibres of different resiliency. For this purpose, an arbitrary number (but equal to at least two) of rollers connected to high voltage are provided I the value of the high voltage for at least one roller being different than that for the other roller or rollers. In this way it is possible for the field intensity in the fibrecoating field to be adapted to the properties of the coating fibres and the support by the voltage at the rollers, and for the residence time for the support to be fibrecoated by adapting the number of rollers and the spacings thereof for an optimum fibre-coating.

The underlying feature of the invention is hereinafter explained by reference to examples and by reference to FIGURES 1, 2, 3 and 4.

FIG, 1 is a schematic illustration of an electrostatic particle applying apparatus according to a preferred embodiment of the invention.

FIG. 2 is a schematic illustration of a portion of the apparatus of FIG. 1 pertaining to the arrangement of the conveyor band therein as modified in accordance with another embodiment of the invention.

FIG. 3 is a schematic illustration of a portion of the apparatus of FIG. 1 pertaining to the arrangement of the web and conveyor band therein, as modified in accordance with a further embodiment of the invention.

FIG. 4 is a schematic illustration of a portion of the apparatus of FIG. 1 pertaining to the arrangement of the conveyor band therein, as modified in accordance with still another embodiment of the invention.

A web 1 which is to be coated with fibres is guided from a drum 2 by way of a roller 3, is coated with adhesive by means of a doctor blade 4 and is then supplied by way of rollers 5, 12 and 13 to a drying duct or tower 22. The adhesive layer of the web 1 is disposed underneath and it is earthed through the applicator device or through the web to be coated by way of the conductive rollers 5, 12 and 13. Fibres 6 for the coating are dispensed from a storage container 7 by means of a rotating brush 8 and through a screen 9 on to a conveyor belt 19.

The run of the conveyor belt 19 is fixed by conductive earthed rollers 14, 15, 16 and 17 of which the roller 15 is driven, while the others are driven by the conveyor belt. The direction of travel of the conveyor belt 19 and of the web 1 can be the same or opposite, and in the example they run in the same direction.

Arranged between the rollers 14 and 17, according to the invention, are three rollers 10, 11 and 23, which can be supplied through separate conductors 24, 25 and 26 with high voltage, and in fact from two high voltage arrangement 20 and 27 in the present case. The voltage for the rollers 10,- 11 and 23 are so adjusted that an optimum fibre-coating is produced. When the web 1 is spaced from the conveyor belt 19 by a distance of for example 15 cm., the roller 10 is connected through the conductor 24 to a high voltage arrangement 27,. the second pole or terminal of which is earthed and the voltage of which is adjusted to 50-100 kv., advantageously about 80 kv. The rollers 11 and 23 are connected through conductors 25 and 26 to a common high voltage arrangement 20, the voltage of which is adjusted to lower values of 30-50 kv. The quantity of fibres delivered to the belt is so regulated that there is practically no excess on the belt after leaving coating zone 21 and a suction device 18 merely has the extract by suction the particles which are firmly adhering. This arrangement has the advantage that the first jumping of the coating fibres is caused by the roller 10 in the stronger field, while the lower field and intensity in the rollers 11 and 23 is sufficient for any further jumping. The high field intensity is restricted to the space above the roller 10 and thus the probability of flashovers is reduced. The voltage at the roller 10 is adjusted to a higher value in proportion as a coating fibre is less satisfactorily erected.

A high voltage at the roller 10 has moreover been provided advantageous when the density of the coating fibres screened on to the belt would have to be made so great, in order to produce a large covering, that the fibres on the belt are more frequently in contact with one another. Finally, the voltage at the roller 10 renders possible an effective proportioning of the coating fibres. For example, if an increase in the quantity of fibres passed through the screen no longer leads to an increase in the application, but only to an increase in the excess remaining on the belt, the application can nevertheless be increased by means of the voltage at the roller 10 without the frequency of spark flashovers becoming impermissibly large on account of an increase in the voltage in the entire fibre-coating field 21.

A modification of the arrangement is shown in FIG. 2. In this case, the zone of higher field intensity has been lengthened by the roller 10 having been replaced by several rollers 10. The rollers 10 are connected to one another and through a common conduct-or 24 to the ranged beneath the earthed rollers 12 and 13, The arrangement of the other roller conducting high voltage remains unchanged and corresponds for example to the arrangement shown in FIG. 1. This embodiment has the advantage that the fibre-coating field 21 and thus also the jumping of the coating fibres is entirely limited to that space between the support and belt in which the said support and belt run parallel.

The following arrangement, as illustrated in FIG. 4, is expedient for a uniform alignment of the coating fibres:

Four rollers 10, 11, 23 and 23' carrying high voltage are provided. The voltage supply of the roller 10 is the same as in FIG. 1; the voltage is for example kv. The rollers 23 and 23' are connected through a conductor 28 to a device 29 with a voltage of for example 45 kv. Finally, the roller 11 is supplied with a voltage of about 20 kv. through another high voltage arrangement,

Above the roller 10, the coating fibres are detached from the belt and for the major part anchored, and in the region of the rollers 23 and 23' there takes place a subsequent fibre-coating, by which the excess is used up. The voltage of the roller 11 is so adjusted that no more fibres are erected in the vicinity thereof, but the fibres leave the fibre-coating zone 21, uniformly aligned by the residual field. It is frequently expedient to lengthen the entry zone for the coating fibres with increased voltage by replacing the roller by a plurality of rollers 10', as in FIG. 2. The same applies in respect of the discharge zone for the fibres from the fibre-coating field in the region of the roller 11.

The rollers can be supplied with voltage in known manner, each by a high-voltage device, by a voltage divider, or with a multiplier circuit, by tapping different stages. In order to reduce the expenditure, it is particularly possible with installations for the fibre-coating of narrow bands or webs 1 for the rollers conducting the high voltage to be fixed, so that the belt 19 slides thereover.

The conveyor belt in this case always has an average conductivity, so that a resistivity between approximately 10 and 111 ohms exists between tworollers which are under different high voltage.

We claim:

1. An apparatus for applying particles of material to a moving web surface coated with an electrically conductive adhesive, which comprises an electrically conductive member maintained at a reference electric potential and disposed for contact with the adhesive coating on the web to establish said coating at a generally uniform electric potential corresponding to that of said reference, guide means disposed for engagement with said web to direct the movement thereof lengthwise along a predetermined path passing through a particle collection zone, a conveyor band of limited electrical conductivity disposed for lengthwise movement along a path extending through said collection zone in spaced-apart relation to web sections passing therethrough and facing the adhesive coating on such Web sections, means operable to deposit particles of material upon said conveyor band for transport thereby into said collection zone, a pair of electrically conductive members disposed for contact with said conveyor band at predetermined separated positions along the movement path thereof, one at a position before the conveyor band entrance to said zone and the other at a position after the conveyor band exit from said zone, both of said conductive members being maintained at said reference electric potential, high voltage electric source means having at least two output terminals of dif ferent electric potential level with respect to said reference potential, and at least three electrically conductive members disposed for contact with said conveyor band at predetermined separated positions along the movement path thereof within said collection zone, at least two of said collection zone conductive members being connected to a common output terminal of said electric source means, and the remainder of said collection zone conductive members being each connected to a pre-assigned output terminal of said electric source means to establish a predetermined electric potential distribution over the length of the conveyor band passing within said collection zone and extending outward therefrom to the contact positions of said conductive members at the reference electric potential, and thereby establish an electric field of corresponding intensity distribution acting between such conveyor band length portion and the adhesive coating on web sections passing adjacently thereto through said collection zone, said electric field being generally confined to said collection zone and having an intensity sufficient to electrostatically accelerate to said adhesive coated Web sections passing through the collection zone for capture thereby particles transported into the collection zone by said conveyor band, said reference potential conductive members serving to aid in confining the electric field to the collection zone and to maintain those portions of the conveyor band external to their respective contact positions at the reference p0- tential and hence at substantially zero potential difference with respect to the adhesive coating of the web.

2. The apparatus according to claim 1 wherein the first conductive member within the collection zone after the conveyor band entrance thereto is connected to the electric source means terminal of highest potential difference with respect to the reference potential.

3. The apparatus according to claim 1 wherein the first conductive member within the collection zone after the conveyor band entrance thereto, and at least one conductive member within the collection zone and consecutively following said first member in the direction of conveyor band movement are connected to the electric source means terminal of highest potential difference with respect to the reference potential.

4. The apparatus according to claim 1 wherein one conductive member within the collection zone adjacent to the conveyor band exit thereof is connected to the electric source means terminal of the lowest non-zero potential difference with respect to the reference potential.

5. The apparatus according to claim 1 including a pair of conductive members maintained at the reference potential and disposed for contact with said web at respective positions along the movement path thereof opposite to the contact positions of corresponding reference potential conductive members of said pair thereof in contact with the conveyor band.

References Cited CHARLES A. WILLMUTH, Primary Examiner. J, P, MCINTOSH, Assistant Examiner, 

1. AN APPARATUS FOR APPLYING PARTICLES OF MATERIAL TO A MOVING WEB SURFACE COATED WITH AN ELECTRICALLY CONDUCTIVE ADHESIVE, WHICH COMPRISES AN ELECTRICALLY CONDUCTIVE MEMBER MAINTAINED AT A REFERENCE ELECTRIC POTENTIAL AND DISPOSED FOR CONTACT WITH THE ADHESIVE COATING ON THE WEB TO ESTABLISH SAID COATING AT A GENERALLY UNIFORM ELECTRIC POTENTIAL CORRESPONDING TO THAT OF SAID REFERENCE, GUIDE MEANS DISPOSED FOR ENGAGEMENT WITH SAID WEB TO DIRECT THE MOVEMENT THEREOF LENGTHWISE ALONG A PREDETERMINED PATH PASSING THROUGH A PARTICLE COLLECTION ZONE, A CONVEYOR BAND OF LIMITED ELECTRICAL CONDUCTIVITY DISPOSED FOR LENGTHWISE MOVEMENT ALONG A PATH EXTENDING THROUGH SAID COLLECTION ZONE IN SPACED-APART RELATION TO WEB SECTIONS PASSING THERETHROUGH AND FACING THE ADHESIVE COATING ON SUCH WEB SECTIONS, MEANS OPERABLE TO DEPOSIT PARTICLES OF MATERIAL UPON SAID CONVEYOR BAND FOR TRANSPORT THEREBY INTO SAID COLLECTION ZONE, A PAIR OF ELECTRICALLY CONDUCTIVE MEMBERS DISPOSED FOR CONTACT WITH SAID CONVEYOR BAND AT PREDETERMINED SEPARATED POSITIONS ALONG THE MOVEMENT PATH THEREOF, ONE AT A POSITION BEFORE THE CONVEYOR BAND ENTRANCE TO SAID ZONE AND THE OTHER AT A POSITION AFTER THE CONVEYOR BAND EXIT FROM SAID ZONE, BOTH OF SAID CONDUCTIVE MEMBERS BEING MAINTAINED AT SAID REFERENCE ELECTRIC POTENTIAL, HIGH VOLTAGE ELECTRIC SOURCE MEANS HAVING AT LEAST TWO OUTPUT TERMINALS OF DIFFERENT ELECTRIC POTENTIAL LEVEL WITH RESPECT TO SAID REFERENCE POTENTIAL, AND AT LEAST THREE ELECTRICALLY CONDUCTIVE MEMBERS DISPOSED FOR CONTACT WITH SAID CONVEYOR BAND AT PREDETERMINED SEPARATED POSITIONS ALONG THE MOVEMENT PATH THEREOF WITHIN SAID COLLECTION ZONE, AT LEAST TWO OF SAID COLLECTION ZONE CONDUCTIVE MEMBERS BEING CONNECTED TO A COMMON OUTPUT TERMINAL OF SAID ELECTRIC SOURCE MEANS, AND THE REMAINDER OF SAID COLLECTION ZONE CONDUCTIVE MEMBERS BEING EACH CONNECTED TO A PRE-ASSIGNED OUTPUT TERMINAL OF SAID ELECTRIC SOURCE MEANS TO ESTABLISH A PREDETERMINED ELECTRIC POTENTIAL DISTRIBUTION OVER THE LENGTH OF THE CONVEYOR BAND PASSING WITHIN SAID COLLECTION ZONE AND EXTENDING OUTWARD THEREFROM TO THE CONTACT POSITIONS OF SAID CONDUCTIVE MEMBERS AT THE REFERENCE ELECTRIC POTENTIAL, AND THEREBY ESTABLISH AN ELECTRIC FIELD OF CORRESPONDING INTENSITY DISTRIBUTION ACTING BETWEEN SUCH CONVEYOR BAND LENGTH PORTION AND THE ADHESIVE COATING ON WEB SECTIONS PASSING ADJACENTLY THERETO THROUGH SAID COLLECTION ZONE, SAID ELECTRIC FIELD BEING GENERALLY CONFINED TO SAID COLLECTION ZONE AND HAVING AN INTENSITY SUFFICIENT TO ELECTROSTATICALLY ACCELERATE TO SAID ADHESIVE COATED WEB SECTIONS PASSING THROUGH THE COLLECTION ZONE FOR CAPTURE THEREBY PARTICLES TRANSPORTED INTO THE COLLECTION ZONE BY SAID CONVEYOR BAND, SAID REFERENCE POTENTIAL CONDUCTIVE MEMBERS SERVING TO AID IN CONFINING THE ELECTRIC FIELD TO THE COLLECTION ZONE AND TO MAINTAIN THOSE PORTIONS OF THE CONVEYOR BAND EXTERNAL TO THEIR RESPECTIVE CONTACT POSITIONS AT THE REFERENCE POTENTIAL AND HENCE AT SUBSTANTIALLY ZERO POTENTIAL DIFFERENCE WITH RESPECT TO THE ADHESIVE COATING OF THE WEB. 